Pretargeted imaging is an emerging technique to study the in vivo biodistribution of nanomedicines. Currently, the tetrazine ligation is considered the most promising bioorthogonal reaction for pretargeting. Recently, Zheng et al. described an ultrafast late-stage radiolabeling of tetrazines based on sulfur 18 F-fluoride exchange click chemistry ([ 18 F]SuFEx). However, bispyridyl and H-tetrazines-the most promising structures for in vivo pretargeted applications-cannot be labeled using the proposed reaction conditions as they lead to decomposition of the tetrazine core. Here, we report improved conditions that allow 18 F-labeling of bispyridyl and H-tetrazines using SuFEx. This strategy resulted in fast and efficient radiolabeling of highly reactive tetrazines with radiochemical conversions of up to 85%. This opens up the possibility to use SuFEx to 18 F-label tetrazines which are suitable for in vivo pretargeted imaging.